1. Field of the Invention
The present invention relates to actuatable fasteners. More specifically, the present invention relates to retention mechanisms for actuatable fasteners that may be used to releasably fasten objects together.
2. Description of Related Art
Actuatable fasteners, such as exploding bolts, are often used to releasably fasten together objects that may need to become unfastened under certain circumstances. Such actuatable fasteners are generally shaped like standard male fasteners, with an elongated fastener body extending from an attached fastener head. Ordinarily, some type of explosive is contained within the fastener body or the fastener head. When the fastened objects are to become unfastened, the explosive is ignited. The resulting explosion causes the fastener head to separate from the fastener body, permitting the fastened objects to become unfastened.
One situation where actuatable fasteners may be used is in connection with airbag systems. Typical airbag systems include an inflatable cushion contained within a housing and an activation device which is configured to sense a collision through the use of a collision sensor, such as a piezoelectric accelerometer. The activation device may utilize acceleration data, alone or in combination with other data, to determine whether the inflatable cushion should be inflated. The activation device may also detect other relevant metrics, such as the impact velocity, occupant weight, occupant position, and the like through the use of additional sensors. These metrics may be used to determine the desired stiffness of the inflatable cushion, which may be adjusted through the use of one or more venting tubes. A venting tube generally extends from the inflatable cushion and is attached to and compressed against the airbag housing by an actuatable fastener.
When an actuatable fastener is used in this manner, the fastener is generally positioned so that the venting tube is compressed between the fastener head and the airbag housing. In this configuration, the venting tube is “closed;” namely, gas from the inflatable cushion is substantially prevented from flowing through the venting tube. When the actuatable fastener is actuated (i.e., when the fastener head separates from the fastener body), the venting tube moves to an “open” configuration and inflation gas can flow out of the inflatable cushion through the venting tube. If the activation device determines that the stiffness of the inflatable cushion should be reduced, the activation device typically sends an activation signal to the actuatable fastener, causing the actuatable fastener to be actuated.
Some type of retention mechanism is generally used to retain an actuatable fastener in a particular location. In the airbag example discussed above, the retention mechanism is generally used to keep the fastener in a position where the venting tube is compressed between the fastener head and the airbag housing, so that the venting tube is maintained in a closed position.
One example of a known retention mechanism is an internally threaded female fastener, such as a nut. With such a retention mechanism, the fastener body is generally manufactured with external threads that mate with the internal threads in the female fastener. To retain the actuatable fastener in a desired position on the airbag housing, the fastener body is generally inserted through a hole in the venting tube and a hole in the airbag housing. The female fastener is then screwed onto the fastener body on the side of the airbag housing opposite the fastener head, and tightened until the fastener is held in place.
Unfortunately, such a retention mechanism requires the use of parts that have been machined to include threads. Machined parts are typically more expensive to produce than parts that are not machined. Moreover, it takes a considerable amount of time to screw the female fastener onto the fastener body, making this type of retention mechanism quite labor intensive. Accordingly, a need exists for a retention mechanism for an actuatable fastener that is less costly to produce and that is easier to install than presently available retention mechanisms.